Novak Djokovic Advances to US Open Quarterfinals with Win over Joao Sousa

Novak Djokovic eased into the quarterfinals of the 2018 U.S. Open with a straight sets victory over Portugal's Joao Sousa on Monday at Flushing Meadows.

The sixth seed found it tough going in hot conditions in New York but prevailed 6-3, 6-4, 6-3 in exactly two hours on Arthur Ashe Stadium.

Djokovic was below his very best and took an off-court medical timeout at the start of the third set. However, he returned to take the win and remains on course for a potential quarterfinal clash with Roger Federer.

Djokovic made a fine start to the match, as he put Sousa under pressure in only his second service game. The Portuguese was forced to save a game point, before Djokovic broke with a superb passing shot to move into a 3-1 lead.

The sixth seed had edged ahead, but he was not quite firing on all cylinders.Metro's George Bellshaw shared his view:

George Bellshaw @BellshawGeorge

Djokovic not looking as slick as he did against Gasquet in the start of this one but still doing enough to draw the errors from Sousa and he breaks for a *2-1 lead with an exquisite backhand passing shot.

Yet Sousa was making little impression on the Djokovic serve, and the Serb broke again to clinch the set 6-3 in 37 minutes.

There was more drama in the second set with Sousa breaking to love to lead 2-1. However, Djokovic hit straight back with Sousa giving up his serve far too cheaply.

The sixth seed was clearly below par, but Sousa continued to make mistakes at crucial times. He was forced to serve to stay in the set at 5-4 and twice hit long to hand the second set to his opponent.

Djokovic was firmly in charge of the match but suffered a wobble at the start of the third set. The Serb said he was struggling with his breathing, according to sports commentator Gigi Salmon, per Saj Chouwdhuryat BBC Sport.

Carolyn Kaster/Associated Press

He then left the court for a medical evaluation with the scores at 2-1, although the precise nature of his problem was unclear.

It seemed to have little impact on the two-time champion who returned and showed no ill-effects as the third set continued on serve.

Meanwhile, Sousa proceeded to get hot and bothered at 4-3. The Portuguese attempted to challenge but saw his appeal turned down by umpire James Keothavong.

Bellshaw noted how the appeal would have made no difference:

George Bellshaw @BellshawGeorge

Sousa absolutely furious over a decision from Keothavong. The umpire claiming it was a late challenge, however, the ball was in anyway so it makes no difference in reality. Of course, they don't know that and the Portuguese was not happy...

The incident certainly riled Sousa who appeared to lose focus. Djokovic immediately pounced to earn himself three break points. He converted the first one to move 5-3 ahead, before serving out the win.

The US Open showed his moment of victory:

US Open Tennis @usopen

Clean sheet for @DjokerNole as he defeats J. Sousa 6-3, 6-4, 6-3 to reach the QF!
He awaits the winner of Federer/Millman...
#USOpen https://t.co/UN4KR3NRRg

Djokovic goes on to play the winner of the fourth-round clash between Federer and John Millman. The Swiss star is the big favorite to progress and set up what will be an eagerly-anticipated tie.